1. Field of the Invention
The present invention relates generally to the treatment of tear fluid or moisture deficiencies in the eye and, more particularly, to punctum plugs and methods of punctal occlusion for deterring the drainage of tear fluid or moisture from the eye.
2. Brief Discussion of the Related Art
Normally the eye is protected and lubricated by a film of naturally produced tear fluid spread over the corneal and conjunctival epithelia through blinking. Various problems may arise in the eye, however, where the quantity of tear fluid or moisture in the eye is deficient, and the problem of insufficient tear fluid or moisture in the eye may be referred to generally as dry eye syndrome or disorder. Tear fluid or moisture deficiencies are oftentimes chronic and may result from inadequate tear fluid production and/or drainage of too much tear fluid or moisture from the eye through the lacrimal drainage system of the eye. Various conditions may cause and/or aggravate tear fluid or moisture deficiencies including disease such as cataracts, inflammation, congenital defects, side effects of over-the-counter and prescription drugs, allergies, environmental irritants or effects, atrophy, aging, eye strain, contact lens use, and procedures performed on the eye such as LASIK and cataract procedures.
Dry eye syndrome is increasing in prevalence and it is estimated that up to 40% of the U.S. population suffers from dry eye syndrome to some extent. Dry eye syndrome may manifest as various ophthalmic ailments including general irritation and/or discomfort, itchy, gritty, sticky and/or burning sensations, conjunctivitis, blepharitis, contact lens problems, corneal erosion, incipient corneal graft rejection, recurrent chalzion, pinguecula, corneal ulcers and acute lid abscesses. Sinus ailments, hay fevers, colds and other recurrent infections have been attributed to dry eye syndrome.
One common treatment for dry eye syndrome involves the introduction of artificial tear fluid into the eye. The benefits derived from artificial tear fluids are limited and are usually of short duration. In some users, artificial tear fluids have caused toxic reactions. Other drawbacks of artificial tear fluids include possible blurred vision and unsightly deposits on the eyelids.
Mechanical devices such as punctum plugs which block or occlude the punctum to deter drainage of tear fluid from the eye have been proposed and are represented by U.S. Pat. Nos. 3,949,750 and 5,283,063 to Freeman, U.S. Pat. No. 4,915,684 to MacKeen et al, U.S. Pat. No. 4,959,048 to Seder et al, U.S. Pat. Nos. 5,723,005, 6,149,684 and 6,290,684 B1 to Herrick, U.S. Pat. No. 5,417,651 to Guena et al, U.S. Pat. No. 5,423,777 to Tajiri et al, U.S. Pat. Nos. 5,741,292 and 6,027,470 to Mendius, U.S. Pat. No.5,830,171 to Wallace, U.S. Pat. Nos. 6,016,806 and 6,041,785 to Webb, U.S. Pat. No. 6,234,175 B1 to Zhou et al, U.S. Pat. No. 6,306,114 B1 to Freeman et al, U.S. Pat. No. 6,344,047 B1 to Price et al, U.S. Patent Application Publication No. US 2004/0254516 A1, and U.S. Patent Application Publication No. US 2005/0197614 A1.
Typically, punctum plugs are implanted in the eye using insertion tools, and punctum plugs having axial passages for releasably engaging the insertion tools have been proposed as represented by U.S. Pat. No. 3,949,750 to Freeman, U.S. Pat. No. 4,915,684 to MacKeen et al, U.S. Pat. No. 5,171,270 to Herrick, U.S. Pat. Nos. 5,283,063 and 5,334,137 to Freeman, U.S. Pat. No. 5,423,777 to Tajiri et al, U.S. Pat. No. 5,723,005 to Herrick, U.S. Pat. Nos. 5,741,292 and 6,027,470 to Mendius, U.S. Pat. No. 5,830,171 to Wallace, U.S. Pat. No. 6,016,806 to Webb, U.S. Pat. No. 6,149,684 to Herrick, U.S. Pat. No. 6,306,114 B1 to Freeman et al, U.S. Pat. No. 6,344,047 B1 to Price et al, U.S. Pat. No. 6,527,780 B1 to Wallace et al, U.S. Patent Application Publication No. US 2004/0254516 A1, and U.S. Patent Application Publication No. US 2005/0197614 A1.
Punctum plugs typically include a proximal head, a distal tip and a shaft connecting the proximal head and the distal tip. The shaft is usually smaller in cross-sectional size than the proximal head and the distal tip. A punctum plug is usually inserted, distal tip first, in a punctal opening of the punctum and is advanced distally in the punctum until the proximal head is seated on the punctal opening. The proximal head is normally larger than the punctal opening such that the proximal head does not pass through the punctal opening and remains exposed in the eye. The distal tip typically has a cross-sectional size to fill the canalicular canal which is in communication with the punctal opening and to anchor the punctum plug in place. Usually the proximal head overlaps and is in abutment with a rim of anatomical tissue circumscribing the punctal opening to better block the punctal opening and prevent displacement or migration of the punctum plug into the punctum. The blockage or occlusion presented by the punctum plug deters tear fluid from draining from the eye through the punctal opening and the corresponding canalicular canal from which tear fluid would otherwise drain into the lacrimal sac and through the nasolacrimal duct into the nasal cavity. The proximal head of the punctum plug remaining exposed in the eye may be engaged with the insertion tool or other instrument by which the punctum plug may be withdrawn through the punctal opening for removal from the eye.
Intracanalicular implants have been proposed which are disposed entirely within the canalicular canal without exposure or protrusion thereof in the eye, and such implants are illustrated by U.S. Pat. Nos. 4,660,546, 5,049,142 and 5,053,030 to Herrick et al, and U.S. Pat. No. 5,163,959 and 5,171,270 to Herrick. Intracanalicular implants which are disposed entirely within the canalicular canal are more difficult to implant and remove, and are more likely to be implanted improperly or to become displaced in the canalicular canal. Accordingly, punctum plugs present advantages over intracanalicular implants as a treatment for dry eye syndrome or disorder.
A problem of many punctum plugs is that they may undesirably or excessively deform or collapse, especially during implantation, due to insufficient structural strength or rigidity. Where a punctum plug undesirably or excessively deforms, collapses or undergoes a “noodling” action during implantation, it is more difficult and time consuming to implant the punctum plug correctly. A punctum plug that undesirably or excessively deforms, collapses or undergoes a “noodling” action during implantation may end up being improperly implanted including implanted too far or not far enough into the punctum, implanted off-center or skewed in the punctum and/or implanted without the distal tip being securely anchored in the canalicular canal. Once implanted, a punctum plug that later excessively or undesirably deforms or collapses due to insufficient strength or rigidity could migrate from its implanted position. An incorrectly implanted punctum plug or one that has migrated after implantation may be less effective at deterring fluid drainage, could cause trauma or discomfort to the patient, and may be more difficult to remove from the eye. It would be desirable, therefore, to increase the strength and rigidity of punctum plugs to resist undesirable or excessive deformation or collapse, especially during implantation.
Another problem of punctum plugs is that the punctum plugs do not well adapt to various different anatomical characteristics found in the puncta of different patients. Depending on the individual anatomy of a patient, the punctal opening may be exposed on the surface of the eyelid or may be introverted on the lid margin and lying against the surface of the conjunctiva of the eye. The punctal opening has a funnel shape which can be essentially circular or, more commonly, non-circular or slit-like. A punctal opening that is non-circular generally has a longer (major) axis or dimension extending lengthwise and a shorter (minor) axis or dimension extending widthwise, with the length and width dimensions varying on an individual patient basis. During insertion of conventional punctum plugs through non-circular punctal openings, undesirable or excessive stress or force may be exerted on the anatomical tissue of the punctum as the narrower width dimension of the punctal opening is widened in order to accommodate the punctum plug. Consequently, implantation of the punctum plug is made more difficult and places the patient at risk of trauma. It would be beneficial for an individual punctum plug to better adapt to a wide range of different anatomical puncta to ease insertion of the punctum plug in puncta having both circular and non-circular punctal openings.
Punctum plugs may be made available in different sizes corresponding to anatomical puncta and canaliculi of different cross-sectional sizes. It is important for maximum effectiveness and proper fit that the correct size punctum plug be selected for implantation in the punctum of a patient. Due to the microscopic size of punctum plugs, however, identifying and selecting a punctum plug of the correct size for a patient is generally time consuming and tedious due to the difficulty involved in distinguishing between different size punctum plugs. It would therefore be advantageous to enable punctum plugs to be visually identified or differentiated by size with greater certainty and in as little time as possible.